Regional innervation of the heart in the goldfish, Carassius auratus: A confocal microscopy study

Authors

  • Cecilia M. Newton,

    1. Department of Medical Neuroscience, Dalhousie University, Halifax, Nova Scotia, Canada
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    • The first two authors contributed equally to this work.

  • Matthew R. Stoyek,

    1. Department of Medical Neuroscience, Dalhousie University, Halifax, Nova Scotia, Canada
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    • The first two authors contributed equally to this work.

  • Roger P. Croll,

    1. Department of Physiology and Biophysics, Dalhousie University, Halifax, Nova Scotia, Canada
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  • Frank M. Smith

    Corresponding author
    1. Department of Medical Neuroscience, Dalhousie University, Halifax, Nova Scotia, Canada
    • Correspondence to: Frank M. Smith, Department of Medical Neuroscience, Faculty of Medicine, Dalhousie University, 5850 College Street, PO Box 15000, Halifax, Nova Scotia B3H 4R2, Canada. E-mail: fsmith@dal.ca

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ABSTRACT

The intracardiac nervous system represents the final common pathway for autonomic control of the vertebrate heart in maintaining cardiovascular homeostasis. In teleost fishes, details of the organization of this system are not well understood. Here we investigated innervation patterns in the heart of the goldfish, a species representative of a large group of cyprinids. We used antibodies against the neuronal markers zn-12, acetylated tubulin, and human neuronal protein C/D, as well as choline acetyltransferase, tyrosine hydroxylase, nitric oxide synthetase, and vasoactive intestinal polypeptide (VIP) to detect neural elements and their transmitter contents in wholemounts and sections of cardiac tissue. All chambers of the heart were innervated by choline acetyltransferase-positive axons, implying cholinergic regulation; and by tyrosine hydroxylase-containing axons, implying adrenergic regulation. The mean total number of intracardiac neurons was 713 ± 78 (SE), nearly half of which were cholinergic. Neuronal somata were mainly located in a ganglionated plexus around the sinoatrial valves. Somata were contacted by cholinergic, adrenergic, nitrergic, and VIP-positive terminals. Putative pacemaker cells, identified by immunoreactivity for hyperpolarization activated, cyclic nucleotide-gated channel 4, were located in the base of the sinoatrial valves, and this region was densely innervated by cholinergic and adrenergic terminals. We have shown that the goldfish heart possesses the necessary neuroanatomical substrate for fine, region-by-region autonomic control of the myocardial effectors that are involved in determining cardiac output. J. Comp. Neurol. 522:456–478, 2014. © 2013 Wiley Periodicals, Inc.

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